The present invention relates in general to the fixation of nitrogen and, in particular, to a new and useful process for the fixation of nitrogen and oxygen to form nitrogen oxides and a nitrate of a solid oxide.
Nitrogen fixation in general is the utilization of atmospheric nitrogen to form chemical compounds. In nature, nitrogen fixation is formed by bacteria located on the root hairs of plants. Industrial nitrogen fixation is exemplified by the production of ammonia using a gaseous mixture containing hydrogen and nitrogen.
The fixation of nitrogen using an alkaline earth metal is known from French Pat. No. 798,224 to Basset. This patent discloses the use of a nitrogen and oxygen mixtures of gases at high temperatures and pressures in the presence of an alkaline earth to form the nitrate of the alkaline earth metal. A similar process is disclosed in U.S. Pat. No. 1,954,415 to Kipper which utilizes temperatures of about 1,000.degree. C. and pressures of 100 atmospheres or higher to produce the nitrates in the presence of a catalyst. A deficiency of these references, however, is that they do not provide for a cycling of the process and must in all cases elevate the temperatures to the operating temperatures of the reaction and maintain that temperature to yield the results disclosed. The methods and reactions disclosed are not suitable for commercialization due to these inadequacies.
Until the early 1940's, the thermodynamics of the nitrogen fixation process were not known. Only in the early 1950's did the thermodynamics become common knowledge in the field. The dissociation of nitrates into nitrogen oxides and the corresponding equilibrium with nitrogen and oxygen were known however, semiquantitatively. The above identified French reference which predated the clear understanding of the thermodynamics of the nitrogen fixation process, describes a reverse process to the dissociation of nitrate and corresponds to the formation of nitrate at high pressures and temperatures.
Other non-anticipating references which are of interest in considering this invention are U.S. Pat. No. 2,578,674 to Daniels et al. for a Nitric Oxide Recovery System, U.S. Pat. No. 3,333,923 to Leatham et al. for a Method For Producing Nitric Oxide, and U.S. Pat. No. 3,911,081 to Maness et al. for the Catalytic Oxidation of Nitric Oxide in Molten Salt.
The fixation of nitrogen has important industrial uses and, while in general utilizing air, the process remains relatively inefficient and expensive.